Turbojet and rocket motor combination with hot gas ignition system for nonself-reaction rocket fuels



Hamil 3 1954 B. W. BRUCKMANN 2,673,445

TURBOJET AND ROCKET MOTOR COMBINATION WITH HOT GAS IGNITION SYSTEM FOR NONSELF-REACTION ROCKET FUELS Filed June 21, 1949 3 Sheets-Sheet 1 IN VEN TOR. Bel/N0 11/. 5 CKMH/V/V Ow Q II Q O 0 o O O Q m. Q

March 30, 1954 B. w. BRUCKMANN 2,673,445

TURBOJET AND ROCKET MOTOR COMBINATION WITH HOT GAS IGNITION SYSTEM FOR NONSELF-REACTION ROCKET FUELS Filed June 21, 1949 3 Sheets-Sheet 2 March 30, 1954 B. w. BRUCKMANN 2,673,445

TURBOJET AND ROCKET MOTOR COMBINATION WITH HOT GAS IGNITION SYSTEM FOR NONSELF-REACTION ROCKET FUELS Filed June 21. 1949 a Sheets-Sheet s Patented Mar. 30, 1954 TURBOJET AND ROCKET MOTOR COMBINA- TION WITH HOT GAS IGNITION SYSTEM FOR NONSELF-REACTION ROCKET FUELS Bruno W. Bruckmann, Greene County, Ohio, assignor to United States of America as represented by the Secretary of the Air Force Application June 21, 1949, Serial No. 100,521

6 Claims.

(Granted under Title 235, U. S. Code (1952).

The invention described herein may be manu factured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

The present invention relates to an aircraft propulsion unit in the form of a turbojet and rocket motor combination with hot gas ignition system for non-selfreacting rocket fuels.

The primary object of the invention is to provide a turbojet aircraft engine having a rocket motor mounted within the central conical portion of the exhaust nozzle of the engine, thus utilizing to good advantage space which might otherwise be wasted.

A further object of the invention is to provide a turbojet aircraft engine having a rocket motor mounted within the central conical portion of the exhaust nozzle of the engine and including means to divert some of the high temperature combustion products from the engine to the rocket motor for initiating a chemical reaction in the rocket motor, which reaction involves the use of nonselfreacting fuels or reactants.

Another object of the invention is to provide a turbojet aircraft engine having a rocket motor fixed in the exhaust section of the engine and including a mechanical coupling between the engine turbine and the pumping units for the rocket motor.

Another object of the invention is to provide a turbojet and rocket motor combination including a control system for the rocket motor whereby hot gas diverted from the turbojet combustion chamber is supplied to the rocket motor only long enough to start the rocket oxidation reaction and is then shut off automatically to prevent loss of efficiency and thrust in the turbojet engine and to prevent rocket oxidation products from flowing into the turbojet combustion chamber.

Another object of the invention is to provide a turbojet engine having a built-in thrust-augmenting unit occupying the central portion of the engine exhaust section.

Another object of the invention is to provide a turbojet and rocket motor combination including a control system for the rocket motor requiring a minimum of attention by the aircraft pilot or flight engineer.

Another object of the invention is to provide a rocket motor for use on aircraft and including a control system having certain automatic features which make the motor particularly useful on air craft.

The above and other objects ofthe invention will become apparent upon reading the following detailed description of the invention in conjunction with the accompanying drawings, in which:

Fig. 1 is a logitudinal cross sectional view taken through a typical turbojet engine and including a rocket motor mounted on the central axis of the engine in the exhaust section thereof. I

Fig. 2 is a diagrammatic view of a control system for the rocket motor and showing the motor in some detail. I

Fig. 3 is a diagrammatic view of a second control system for the rocket motor and showing a second form of motor in some detail.

The preferred embodiment of the invention is best illustrated by reference to Fig. 1, showing a turbojet engine in longitudinal cross section. The engine proper comprises a double-walled housing I of circular cross sectional shape open at the forward end to provide an air intake 2. The air entering the housing passes around the accessory housing 3, also called the island. The housing 3 and parts therewithin are supported by two or more struts 4 of hollow section, through which pass various control wires and conduits such as the fuel lines 5. The air after passin housing 3 is compressed by an air compressor 6 having rotor elements I turning with the engine main shaft 8. The compressed air flows into the combustion chambers 9 arranged around the engine, where it supports combustion of the engine fuel flowing from the fuel lines 5. The products of combustion plus some excess air flow through the gas turbine 10 to cause rapid rotation of the turbine, main shaft and compressor rotor. The hot exhaust gases then flow freely through the annular exhaust nozzle II and are discharged into the atmosphere rearwardly thereof. The propulsive effect of the turbojet engine is due to the large increase in volume of gases in the combustion chamber due to burning of fuel and rapid rise in temperature of the gaseous products of combustion. Thus the engine receives considerably less volume of air per unit of time than is discharged, since the exhaust products are at very much higher temperatures than the incoming air.

On the central axis of the engine and supported by hollow struts I2 there is a tapered housing l3 within which is mounted a rocket motor I 4, discharging rearwardly in a manner similar to the turbojet engine. Since the rocket fuels selected may not be of the self-reacting type, a hot gas diversion pipe [5 is provided to carry heated gases from one of the combustion chambers 9 to the rocket motor [4. The hotgas so divertedflows into the rocket motor chamber through the small forward end thereof, which is provided with the starting valve ['6 slidably mounted by means of a rigid stem H. The stem is pivoted to a lever l8 which is in turn pivoted at [9 to a fixed bracket. The lever I8 is actuated by a rod 20 connected to an actuator 2|. Connected by a clutch 22 to the main shaft 8 there is a gear reduction unit 23 driving the fuel pump 24 and the oxidizer pump 25. The two pumps feed fuel and oxidizer to the rocket motor by way of fuel lines, whereby a violent reaction takes place in the motor chamber involving rapid oxidation of fuel and outward flow of large volumes of gaseous rocket propellants. The fuel used may be kerosene as used also in the turbojet engine and the oxidizer may be concentrated nitric acid (HNOa). The oxidizing reaction therebetween is not self-starting and as a result hot gas flow from the engine must be relied on to bring the temperature in the rocket chamber up to or above approximately 250 C. Then when the fuel and oxidizer are started flowing into the chamber a reaction is started which is rather complex but which does result in rapid oxidation of the hydrocarbon fuel (kerosene) with the evolution of heat. The volumes of gaseous oxidation products flow rapidly from the motor I4 to give greatly increased thrust on the combination turbojet engine and rocket motor. Preferably the rocket motor is only maintained in operation for short time periods, such as during take ofi of the aircraft or during climb maneuvers. Furthermore after the reaction is started in the rocket chamber, the valve 16 must be closed to prevent flow of high pressure gases from the rocket chamber to the combustion chamber 9. As will be explained below this valve closing action is preferably made automatic, in response to increase in the temperature or pressure within the rocket chamber.

Referring now to Fig. 2 there is shown one form of control system for the rocket motor and also some details of the motor itself. The motor l4 receives hot gases from the turbojet engine by way of the conduit I and poppet valve I6, the gases entering at the end of the motor chamber remote from the open discharge end thereof. The valve [6 includes a rigid valve stem or guide member I! extending to a lever 18 which is pivoted at E9 to a fixed support. The lever is actuated by a rod extending into a special hydraulic actuating unit 2| and connected therein to a piston 30. The piston is movable in one direction to close poppet valve It by means of a spring 3! and is movable in the opposite direction to open poppet valve I 6 by action of hydraulic fluid flowing into cylinder 32 by way of side passage 33. Closing of the valve I6 is accomplished by closing the passage 33 and opening a small caliber fluid return passage 34 to permit the spring 3| to move the piston 30 toward the outlet end of the cylinder 32. The slow rate of closing of valve 16 as fluid passes through the return passage 34 will allow the reaction between the fuel and oxidizer to become well started before the flow of hot gases to the reaction chamber is cut off. The closing action of the valve I6 is further assisted by another coil spring 35 mounted in a housing 35 and bearing on a disk 31 secured to the valve stem I1. Control over the fluid supply to cylinder 32 is provided for by a slide valve 33 slidably mounted in a cylinder 39 of the control unit 2 I. The valve member 38 is adapted to close off either of the passages 33 or 34, and is retained in the position shown by a compression spring 40 surrounding the rod or stem 4| extending outwardly for actuation in the direction of the arrow by means of a solenoid 42. Thus the solenoid is adapted to move the valve 38 to a position closing the fluid supply passage 33 and opening the fluid return passage 34, upon actuation of the solenoid by an electrical circuit including a source of electrical potential B and three switches to be described. One of these switches indicated at 43 is responsive to an elevated temperature corresponding to the temperature required to start the rocket reaction, the switch closing at such elevated temperature. As shown the switch 43 has a portion fitting inside the reaction chamber near the hot gas inlet. Numerous kinds of temperature responsive switches may be used but for purposes of illustration reference is made to the U. S. Patent No. 2,373,857 to J. Smith for a detailed showing of a reliable and sensitive switch suitable for use in this installation.

The fuel and oxidizer supply system for the rocket motor includes a clutch 22 for applying engine power to a reduction gear 23 through which power is applied to the fuel pump 2 and to the oxidizer pump 25. The fuel and oxidizer under pressure flow by way ofconduits 44 and 45 to the rocket motor through the valves 43 and 1. Fuel may flow into an annular manifold 53 around the motor It and thence through numerous apertures or nozzles 59 into the rocket chamber. Oxidizer may flow into the annular cavity 58 extending throughout the length of the motor 4 and thence through numerous apertures or nozzles 51 into the rocket chamber. The valves 46 and M are normally retained in closed position by means of a link 52 connected to the valve actuating arms 53 and 54, the spring 55 exerting a constant pull on the link to retain it in the valve off position. The valves are moved to open position by means of a solenoid 56 acting on one end of link 52 to move the link in the direction of the arrow. The solenoid 55 is in series with the battery B, switches 33, 5? and 53 as Well as solenoid 42. The switches 5? and 55 are responsive to fuel and oxidizer pressures respectively to close and perform their part in closing the power circuit to solenoids 42 and 55. These pressure switches or pressurestats ensure that the supply valves .6 and d? will not open until there is pressure on the fuel and oxidizer and also ensure that the hot gas valve it will not close until the fuel and oxidizer are ready to flow into the reaction chamber of the rocket motor. As illustrated in Fig. 2 these pressure switches may each comprise a small fluid receiving chamber covered on one side by a diaphragm which will bulge under pressure to close an electrical circuit. It should be noted also that the annular chamber 50 in the rocket motor extends throughout the length of the reaction chamber, so that the oxidizer will be preheated and the chamber walls will be cooled slightly at the same time. In order to actuate the clutch 22 to the driving condition thereof, a hydraulic actuating cylinder 60 is connected to the pressure and return line 6! and 62 which also supply the valve actuating unit 2|. In the cylinder Ell there is slidably mounted a piston 53 which carries a piston rod fi l, the latter in turn being pivoted to a lever 65 mounted on a fixed pivot 56. The other end 6! of the lever 35 is adapted to force the clutch plates together and provide a driving connection from the engine shaft 8 to the gear reduction unit 23.

The operation of the control system is very simple, since as will be seen the system may be placed in operation by turning on the control valve I to start the servo-fluidv flowing pressureline it. The fluid will flow to cylinder 39 of valve actuatingv unit 2| and, thence by way of passage 33- to cylinder 32. The piston 30 will then be forced outwardly to the position shown and the hot gas valve I6 will be opened accordingly. Assuming that the turbojet engine is running in normal manner, the hot gas diverted along conduit I15 will begin heating up. the rocket motor very rapidly. At the-same time the unit 21 is actuated by pressure in line BI, the fluid pressure will also actuate the piston 63 to apply power .tothe fuel-oxidizer supply system. Since the pumps 24 and 25 will now start operating the pressure switches 51 and 58v will close. After the temperature responsive. switch 43 closes in response to a rise in temperature in the, rocket chamber, the circuit will be completed to the solenoids 42 and 56. Immediately the. fuel and oxidizer valves 46 and 41 will be opened and the piston 39 of servo-unit 2| will close the passage 33 and open the passage 34. The fuel and oxidizer will now flow into the reaction chamber where hotv gas is still flowing by way of valve I6. The high temperature reaction between the fuel (kerosene) and oxidizer (HNOs) will start immediately and will maintain itself in operation due to the heat generated by the reaction. Oxidation of the kerosene or other fuel occurs by combining with the oxygen in the oxidizer, the heat being required to start decomposition of the oxidizer into its components for release of the oxygen into an available form. The oxygen so obtained is in a nascent state and thus provides a more active oxidizing agent than if furnished from an ordinary gas storage tank or from air. The reaction thus proceeds with the evolution of heat and gaseous products of oxidization. The reaction products represent a tremendous increase in volume over the liquids entering the chamber by nozzles 49 and so that the motor provides a large thrust as the reaction products blow out. of the open end of the reaction chamber. After the rocket motor has been in operation long enough to perform its required thrust augmenting function, the manual valve I0 is shut oif. This causes the clutch servo-unit to be deenergized and power is thus disconnected from the fuel and oxidizer pumps. It is noted that any fluid ahead of the piston 63 when the valve I0 is closed will be displaced by action of spring 63' and by leakage past the piston 63 this fluid will gradually escape to the fluid return line connected to the right-hand end of the cylinder 60. The pressure switches 51 and 58. then open to de-energize the solenoids 42 and 56. The valves 45 and 4! then close under action of the spring 55, and the valve 30 returns to the posi tion shown under action of the spring 40. The valve I6 being already closed, no further action will occur with respect to this element and parts connected thereto. The positions of the parts as illustrated corresponds to a condition wherein the valve 70 has just been turned on, but the circuit including switches 43, 51 and 5B and solenoids 42 and 56 has not yet been closed by the automatic means associated therewith.

Referring now to Fig. 3 there is shown a second or alternate form of control system for the rocket motor and also some details of a slightly different rocket motor. The motor I4, of which only the forward end is shown, receives hot gases from the turboiet engine by way of the conduit I5 and poppet valve It. The conduit opens into a combined valve chamber and gas inlet chamber II- within which is mounted a central valve guide I2 to slidably mount the hollow valvev stem 13. The valve stem connects. by an actuating bellows I4 to a fitting I5 adapted to receive liquid fuel under pressure from the line H5. The valve I6 has a small fuel aperture 11 in the mushroom head thereof to inject some fuel as soon as the valve opens by reason of pressure applied to the actuating bellows I4. The bellows has one end secured directly to the hollow valve stem and the other end secured to a stationary part on the fitting I5,

so that when the fuel in the line I6 is put under pressure the bellows will expand lengthwise and move the poppet valve I6 to open position. When the pressure is released the bellows will have enough resiliency to collapse and. again close the valve I6. If desired an assist spring may be associated with the valve stem to ensure closing of the valve It when the pressure in line I6 is relieved. Such a spring would be similar in function to the spring 35 of Fig. 2.

The rocket motor further includes a tapering forward end portion I8 connected by bolts I9 to a cylinder open at the end which is not shown and preferably tapering slightly, as shown in Fig. 1, to better fit the space available in the exhaust section of the engine. The end portion I8 is provided with interconnecting annular recesses BI and 8| through which; circulates liquid oxidizing agent flowing in from the pipe 82. A row of nozzles or apertures 83 per-- mits oxidizer to flow into th reaction chamber. An annular exterior manifold 84 integral with the wall of portion 18 receives liquid fuel from pipe 85, while a row of nozzles 86 carries the fuel from the manifold into the reaction chamber. Extending into the reaction chamber are pressure sensing tubes 81 and 88 leading to a low pressure and a high pressure switch respectively.

The fuel and oxidizer supply system for the rocket motor I4 includes a clutch 22 for applying engine power to a reduction gear 23 through which power is applied to the fuel pump 24 and to the oxidizer pump 25. The fuel and oxidizer under pressure flow by way of conduits 94 and 95 to the rocket motor through the valves 96 and 91. The valves 96 and 91 are normally retained in closed position by means of a link 98 connected to the valve actuating arms and I00, the spring IOI exerting a constant pull on the link to retain it in the valve off position. The valves are moved to open position by means of a sole-. noid I02 acting on one end of the link 38 to move the link in the direction of the arrow. The solenoid I02 is in series with a source of electric power and switches I03, I04 and I05. The latter switch responds to moderate pressure in the reaction chamber to close. The switches I03 and I04 are responsive to fuel and oxidizer pressures respectively to close and perform their part in closing the power circuit to the solenoid I02.

Connected between the fuel pressure line 16 and the line Itf is a pressure cut-off bypass I0! having a valve I08 therein. The valve I08 is normally retained in closed position by a spring I09 acting on the valve arm I I0. The valve is moved to open position by the rod III extending into solenoid I I 2 and is adapted to be closed after a short time interval by a time delay mechanism incorporated in the valve. Va ves ha in ian automatic delayed closing action are commonly "used in flushing toilets and such valves are readily adapted for use in the present apparatus. An example of such an automatic valve is the construction shown in Patent No. 1,624,130 granted to Thomas R. Beggs on April 12, 1927. Opening of the bypass valve for a brief time relieves the pressure in bellows 14 allowing the hot gas valve I to close immediately, due partly to gaseous pressure in the rocket chamber. Once the valve It becomes closed the pressure in the rocket chamber will maintain it closed even though there is pressure in the valve actuating bellows I I. The circuit to solenoid II2 includes a pressure switch I I5 which responds to a higher pressure than that which acts on switch I05. Thus the bypass I01 can not open until oxidation is well started in the rocket chamber and there is no more need for hot gas flow through valve I6. In the fuel pressure line It there is provided a throttle valve or metering valve IIG so that only enough fuel flow will reach the valve I6 to supply the fuel spray aperture T and also maintain sufiicient pressure in the bellows is to hold the valve I6 open. Thus when the bypass I01 is opened the pressure in line I6 will be reduced for a short time interval to nearly zero without seriously affecting the fuel pressure in line 9-2 leading to the valve 98 and to the rocket motor. In order to actuate the clutch '22 to the driving condition thereof, a hydraulic actuating cylinder I is connected to the fluid pressure and return lines I2! and I22. In the cylinder I20 there is slidably mounted a piston I23 which carries a piston rod I24, the latter in turn being pivoted to a lever I25 mounted on a fixed pivot I25. The other end I2! of the lever I25 is adapted to force the clutch plates together and provide a driving connection from the engine shaft 8 to the gear reduction unit 23.

Attention is again directed to the hot gas valve I6 of the rocket motor. The fuel injection aperture II in the head of valve I6 allows flow of liquid fuel through the valve stem and valve head for cooling the valve and thus preventing serious oxidation of the metal wall thereof. Furthermore this fuel flow continues all the time the rocket motor is in operation, even after the valve I6 closes. This is because the throttle valve H5 will always permit limited fuel flow from the line 94 as long as the fuel pump is running and fuel remains in the fuel tank. The fuel issuing from the aperture 'I'I produces a central flame pro- J'ected through the rocket reaction chamber to produce additional heat for primary ignition of the rocket reactants. This flame starts as soon as the valve I3 is opened, since the hot gas from combustion chamber 9 will ignite the fuel and will also carry sufficient excess air to support combustion of the fuel jet from aperture II. of course there is a brief interval of time when the bypass valve I08 is open during which the fuel pressure in the line I3 is reduced to allow closing of the valve I6 and during this interval of several seconds fuel flow through the aperture 'II subsides. It should be noted that the bellows 74 is sufficiently resilient to maintain the hot gas valve I6 closed at such times as the rocket motor is not in use.

As in the first form of control system operation of the rocket motor may be started by turning on the main control valve I to start the servofluid flowing in pressure line I2I. The fluid will flow to cylinder I20 and thus actuate the servopiston I23 to apply engine power to the fueloxidizer supply system. Since the pumps 24 and 25 will now start operating, the pressure switches I03 and I04 will close and fuel pressure will be applied to valve actuating bellows I4 to open the hot gas valve I6. The flow of hot gas into the reaction chamber of rocket motor I4 and the propagation of primary ignition flame due to fuel flow from the aperture II will provide sufficient pressure to close the pressure switch I05 and thus complete the power circuit to solenoid I02 by way of switches I03 and I04. The fuel and oxidizer valves 93 and 91 will now open to feed additional liquid fuel and oxidizerto the rocket motor. The reaction chamber having been preheated-andthere being present the primary ignition flame, the reaction between the fuel and oxidizer will be started and once started will provide heat to maintain itself in operation. The increase in chamber pressure after starting the reaction between the rocket reactants will soon close the pressure switch I I5, to complete a power circuit to the solenoid H2 and thus opening the bypass valve I08 for a brief time. The momentary reduction of fuel pressure on bellows I4 to nearly zero will cause the hot gas valve I6 to close, thus stopping further hot gas diversion through the pipe IS. The rocket propelling reaction will now continue in operation until the fuel and oxidizer are used up or until the operator shuts off servo-fluid valve I30. In case the valve I30 is closed, the clutch 22 will become disengaged and the pumps 2d and 25 will stop. The pressure switches I03 and I04 will nowopen and the solenoid I02 will be de-energized. The fuel and oxidizer valves 96 and 91 will be closed by spring IOI. By stopping the flow of fuel and oxidizer to the reaction chamber, the pressure therein will return to zero and the pressure switches I05 and I I5 will open. Thus all control elements are now in the original condition before operation of the rocket motor. It is noted that any fluid ahead of the piston I23 when the valve I30 is closed will be displaced by action of spring I23 and by leakage past the piston I23 this fluid will gradually escape to the fluid return line I22.

It is noted that the system of Fig. 3 includes pressure switches I05 and H5 to sense the flow of hot gas from the engine and the starting of the rocket propelling reaction respectively. However in accordance with the system of Fig. 2 these pressure-responsive switches may if desired be replaced by temperature-responsive switches. While the present description refers to only one particular combination of fuel and oxidizer it should be understood that the same apparatus will function as stated above with other rocket reactants, particularly those of the nonselfreacting kind. The main engine as illustrated is a typical turbojet type but as will be understood it may be any kind of engine using a combustion chamber and gas turbine.

In closing it is desired to outline some of the advantages and features of the present combination power plant. These are:

(1) Minimum of added weight by combining the rocket motor with a turbojet engine in the manner disclosed. Space requirements also are held to a minimum since the rocket motor occupies space in the engine which may normally not be used at all.

(2) Addition of the rocket motor entails the least number of added parts and auxiliaries, especially since power and hot gas is, available from the engine. Even the gear reduction unit may be 9 Omitted in some cases, with the engine driving the pumps directly.

(3) simplification of the fuel system for the rocket motor by use of the same fuel in engine and rocket motor, thus resulting in fewer tanks, conduits and valves as well as easier servicing of the power plant.

(4) Combined engine and rocket motor is more easily serviced and overhauled because the complete power plant is capable of being'dismounted as a single unit.

(5) Coincidence of thrust axes of the engine and the rocket motor simplifies aircraft control because of absence of any turning moments due to spaced apart power units.

The embodiments of the invention herein shown and described are to be regarded as illustrative only and it is to be understood that the invention is susceptible of variations, modifications and changes within the scope of the appended claims.

I claim:

1. In a turboiet aircraft engine including in consecutive series an air compressor, a, plurality of combustion chambers, a gas turbine and an exhaust section providing an annular exhaust passage coaxially located with respect to said engine, a rocket motor including an open-ended housing forming a reaction chamber, means mounting said housing centrally of said exhaust section and within the circular space inside of said annular exhaust passage, means for conducting limited volumes of hot exhaust gases from at least one of said compustion chambers to said reaction chamber, means for feeding rocket reactants to said reaction chamber to produce a flow of gaseous reaction products for discharge from the open end of said housing in the same direction as the exhaust gases flowing through and out of said annular exhaust passage from the engine, means for starting the flow of hot gases to said reaction chamber before the flow of rocket reactants thereto is started, and means responsive to initiation of the rocket reaction involving said reactants for stopping further flow of hot gases into said reaction chamber.

2. In a turbojet aircraft engine including in consecutive series an air compressor, a plurality of combustion chambers, a gas turbine and an exhaust section providing an annular exhaust passage coaxially located with respect to said engine, a rocket motor including an open-ended housing forming a, reaction chamber, means mounting said housing centrally of said exhaust section and within the circular space inside of said annular exhaust passage, means for conducting limited volumes of hot exhaust gases from at least one of said combustion chambers to said reaction chamber, means for feeding rocket reactants to said reaction chamber to produce a flow of gaseous reaction products for discharge from the open end of said housing in the same direction as the exhaust gases flowing through and out of said annular exhaust passage from the engine, means for starting the flow of hot gases to said reaction chamber before the flow of rocket reactants thereto is started, means including a temperature responsive switch and a solenoid for stopping further flow of hot gases into said reaction chamber.

3. In a turbojet aircraft engine including in consecutive series an air compressor, a plurality of combustion chambers, a gas turbine and an exhaust section providing an annular exhaust passage coaxially located with respect to said sm rt engine, a rocket motor including an open-ended housing forming a reaction chamber, means mounting said housing centrally of said exhaust section and within the circular space inside of said annular exhaust passage, means providing a valve in the "end of said housing opposite to said open end, means for conducting hot exhaust ases from at least one of saidcombustion chambers to said valve means, means including pumps driven by said turbine for feeding fuel and oxidizer in liquid forms to said reaction chamber to produce a flow of gaseous reaction products for discharge from the open end of said housing in the same direction as the exhaust gases flowing through and out of said annular exhaust passage from the engine, means to open said valve means at the same time said pumps are set in operation, and means including solenoid actuated valves to start the flow of fuel and oxidizer into said reaction chamber after the flow of hot air thereto has been started.

4. In a turbojet aircraft engine as recited in claim 3, and further including means responsive to initiation of the rocket reaction involving oxidation of said fuel for stopping further flow of hot gases into said reaction chamber.

5. In a turbojet aircraft engine including in consecutive series an air compressor, a plurality of combustion chambers, a gas turbine and an exhaust section providing an annular exhaust passage coaxially located with respect to said engine, a rocket motor including a housing of circular cross-section open at one end and forming a reaction chamber, means mounting said housing centrally of said exhaust section so as to substantially fill the circular space within said annular exhaust passage with the open end of said housing facing in the same direction as the discharge end of said annular exhaust passage, means for conducting limited volumes of hot exhaust gases from at least one of said combustion chambers directly to said reaction chamber, means for starting the flow of hot gases to said reaction chamber before the flow of rocket reactants thereto is started and means for feeding rocket reactants to said reaction chamber to produce a flow of gaseous reaction products for discharge from the open end of said housing in the same direction as the exhaust gases flowing through and out of said annular exhaust passage from the engine.

6. In a turbojet aircraft engine including in consecutive series an air compressor, a plurality of combustion chambers, a gas turbine and an exhaust section providing an annular exhaust passage coaxially located with respect to said engine, a rocket motor including a housing of circular cross-section open at one end and forming a reaction chamber, means mounting said housing centrally of said exhaust section so as to substantially fill the circular space within said annular exhaust passage with the open end of said housing facing in the same direction as the discharge end of said annular exhaust passage, means for conducting limited volumes of hot exhaust gases from at least one of said combustion chambers directly to said reaction chamber, means for starting the flow of hot gases to said reaction chamber before the flow of rocket reactants thereto is started and means including pumps driven by said gas turbine for feeding rocket reactants to said reaction chamber to produce a flow of gaseous reaction products for discharge from the open end of said housing in the same direction as the exhaust gases flowing through and out of said annular exhaust passage Number from the engine. 2,443,250 7 BRUNO W. BRUCKMANN. 2,482,819 2,531,761

References Cited in the file Of this patent 5 UNITED STATES PATENTS Number Number Name Date 919,127 2,382,564 Haverstick Aug. 14, 1945 93 ,133 2,404,335 Whittle July 16, 1946 594,207 2,419,866 Wilson Apr. 29, 1947 246,173

12 Name Date Johnson June 15, 1948 Williams Sept. 27, 1949 Zucrow Nov. 28, 1950 FOREIGN PATENTS Country Date France Nov. 18, 1946 France Feb. 16, 1948 Great Britain Nov. 5, 1947 Switzerland Sept. 1, 1947 

